Aero propeller



NOV. 4, 1930. C. MCCARROLL I 1,780,431

AERO PROPELLER Filed Qca, 8, 1925 s sheets-sheet l g'nwcnl'ol QHHRLES MCQHRROLL C. MCCAR ROLL AERO PROPELLER Nov. 4, 1930.

. Filed Oc't. 8' 1925 5 Sheets-Sheet 2 gllvcnt/Qt cHnRLEs MccRRoLLCUTCIIKMJ Nov. 4, 1930. c.' MCCARROLL AERO PROPELLER Filed Oct. 8' i9255 Sheets-Sheet Patented Nov. 4, 1930 l CHARLES MGCARROLL, F HELENA,ALABAMA AERO PROPELLER Application led October 8, 1925. Serial No.61,320. .v

My invention relates to propellers for operating in any Huid mediumwherein it is contemplated that a high efficiency will result from theprovision of automatic means to cause .the air or fluid medium to strikethe forward edge of the curved revolving impeller blades in eXacttangency.

Various conditions will affect the angle of y approach of the currentsof the air, which as hereinafter referred to is to be regarded asinclusive of any fluid medium, to the forward edge of the curvedimpeller blades, and I have conceived that means, such as a vane pilot,can be employed to control suitable operating mechanism which willautomatically eftect the angular adjustment of the blades about theirlong axes so as at all times to preserve the status of tangency betweenthe air currents and the forward edge of the impeller blades. My presentinvention covers broadly such an idea and also a preferred arrangementof the vane pilot and its controlled mechanism for the adjustment of theblades. V

My invention also comprises certai'n new and useful improvements in thedetail structure of impeller blades and'contemplates the formationofeach blade by two outwardly convergent concavo-convex blades joined attheir base to any suitable support mounted on the impeller shaft.

My invent-ion further contemplates the provision at the tip of the bladeof a reinforcing angle set at right angles to the axis about which itsrespective blade turns in being adjusted, the flange of the angle beingturned rearwardly or in the direction of the movement of the propelledmedium. This tends to prevent the radial slippage of the fluid mediumover the impeller blade due to its inclination as well as tocentrifugalforce, and gives the blade a more eilicient vision ofelectrically-controlled means, responsive to displacement of a vanepilot, for actuating the transmission mechanism and ad'usting theblades.

y invention further contemplates a very 1 s simple and effectivearrangement of a bladecontrolling vane pilot by means of which it isrendered sensitive only for the diversion of the air current from aposition of tangeney and is entirely unaffected by centrifugal force.This is attained by correctly mounting the vane pilot on an impellerblade support or disk, revoluble with the impeller blade on its axis,the vane pilot shaft defining a cone with its vertex at the point ofintersection of the impeller axis and the propeller shaft when theimpeller blade is revolved on its axis. Such an arrangement makes theeffectiveness ofthe vane pilot unchanged by the various positionsassumed throughout its controlling function.

My invention further comprises the novel details of construction andarrangements of parts, which are hereinafter more particularly describedand 'pointed out in the claims, 75 reference being had to theaccompanying drawings which form a part of this s eciication, and whichillustrate the pre erred embodiment only of my invention.

According to the drawings Fig. l is a side elevation of my improved aeropropeller mechanism. l

Fig. 2 is a front view of Fig. 1 with the propeller blades partly brokenaway.

Fi .13 is a diagrammatic view of the electrica circuits for theautomatic blade adjustment.

Fig. 4 is a longitudinal cross-sectional view taken on the broken line4-4 of Fig. 2.

Fig. 5 is a cross-sectional view taken on the 90 line 5 5 of Fig. 1.

Fig. 6 is a longitudinal 'detail cross-sectional view of one of thepropeller blades.

Fig. 7 is a diagrammatic view showing, by way of-example, a typicalrepresentation of the relative direction of approach of the propellerblades to, and of their departure from, the fluid medium in which theyare operated; and

Fig'. 8 is a graphic representation of the 100 direction and velocity ofthe propeller blades, the direction and velocity of the fluid currents,and the relative direction and velocity of the fluid currents when thepropeller is operating as shown in Fig. 7

Similar reference numerals refer to similar parts throughout thedrawings.

In the embodiment of my invention illustrated, which in Fig. 1 may beconsidered as being applied to a pusher type airplane, I showconventionally a motor 1 having its shaft 2 connected by a coupling 3 tothe main tubular propeller shaft 4, which is threaded at' its outer endand has screwed and keyed thereon the hub 5 of the propeller spider.This spider, as will be more clearly seen in Figs. 2 and 4, comprisesradial spokes 6 integral with the web 7 and extending from the hub tothe outer peripheral flange 8, which flange is concentric with an innercircumferential flange 9. A master gear 10 is secured on a gear wheel 11mounted so that it can turn on the reduced outer end 5 of the propellerspider hub. A nut 12 secures the master gear assembly in position on thespider. The master gear has its bevelled teeth facing rearwardly ortowards the motor and adapted to be engaged by a series of impellershaft pinions 13, which are mounted fast o'n tubular impeller shafts 14disposed radially of the spider and having suitable bearings in thespider flanges 8 and 9. The spider web is cut away opposite each bevelpinion 13 so that the teeth of the latter can project. forwardly throughthe web to engage the master gear. These cut-outs are indicated at 15 inFig. 4. Each impeller shaft, at its outer end beyond the flange 8,receives a circular impeller blade disk 16, upon each of which animpeller blade, which will be later described in detail, is mountedradially of the spider.

The impeller blades are formed by two concavo-convex plates 17 and 18which are set so that they converge at their outer ends and are joinedthere, being riveted together through a reinforcing angle 19 set withits flange 20 disposed rearwardly. Theinner ends are riveted to aflanged plate 20a secured to the blades disk 16 (see Fig. 6). One of theimpeller blade disks is provided with a pilot base 21, formed integrallytherewith or suitably attached thereto and projecting beyond itsperiphery at an angle so that the inner end 22 of a pilot shaft ispivotally secured in this carrier in radial relation to the spider wheelso that as it swings it will define a, cone having its apex at the pointof intersection of the axes of the propeller and impeller shafts. Theouter end of the pilot shaft, indicated at 23, is bent through an arc of90, and has secured at its end a V-shaped vane pilot 24 disposed withits apex lying in the lane of the pilot shaft and with its axis para lelwith the shaft end 22. The

pilot will travel just in advance of the propeller blade that is mountedon the disk 16 carrying the pilot base 21. The end 22 of the pilot shafthas a circuit-closing stem 25 projecting inwardly between the blades ofthe adjacent impeller and adapted to co-act with a pair of contacts 26and 27, shown in the electrical diagram in Fig. 3, and which aredisposed between the propeller blades in such relation to the pilotstein that the latter will stand midway between the contactswhen the airstrikes the impeller blades at true tangency. As the air tends to departfrom true tangency the pilot will revolve about its shaft vend 22 asanaxis and will swing the stem 25 until it engages contact 26 or 27,thereby closing control circuits which will be later described.

The impeller shaft carrying the pilot 1s provided at its inner end withthree collecting rings 28, 29 and 30, connected by circuits 31, 32 and33, respectively, to the contact 26, the circuit closing arm 25, and theContact 27, as will be seen more clearly in Fig. 3, these circuitsrunning through the hollow propeller sh'a'ft for the spider. Brushes 34,35 and 36, respectively, engage the collecting rings'28, 29 and 30 andare connected by circuits 37, 38 and-39 to the collector rings 40, 41and 42 mounted on the propeller shaft and respectively engaged bybrushes 43, 44 and 45. The brush 43 is connected by a circuit 46 to oneend of a battery 47, the other end of which battery is connected by acircuit 48 with the brush 45. The battery at its neutral point isconnected by a circuit49 with the brush 44. A dynamo is connected by theleads 50 to the battery and a switch solenoid 51 is interposed in thecircuit 49 and adapted to control a double-throw switch 52, which bycircuits 53 and 54 from the batteries are adapted to control theenergization of a set-works solenoid 55. By the circuit arrangementshown the battery circuits are controlled by the pilot stem 25 toattract or repel the double-throw switch 52 'and connect the battery tothrow the current in the desired direction through the set-workssolenoid and thereby to retract or repel its core which controls the setworks.

The various circuits described are carriedv on or through the rotatingparts in any practical manner, and are omitted in detail from theconstruction drawings to avoid confusion.

Referring to Figs. 1 and 4, it will be seen that the propeller shaft ismounted in spaced bearings 56 and 57, which are connected by 'tubularframe members 58 and 59. To the parallel legs of the frame 58 standingradially to the propeller shaft, I clamp a channel iron 60, which hasits web cut away so that its top and bottom flanges will straddle theframe ends and receive the clamping bolts on each side thereof. To theintermediate portion of both top and bottom flanges, I pivotally mount apantograph frame-work comprising upper bars 61, lower bars 62, and uplper and lower intermediate connecting bars 63 and 64, respectively. Theupper and lower bars 61 and 62 of each pair have their free ends drawntogether at an angle (see Fig. 5), and are riveted together with the endof one bar projecting suiiciently' for pivotal connection to theadjacent end of the core 65 of the set-works solenoid which forms theouter connecting member of the pantograph. I mount brackets 66 and 67 onthe opposite pairs of pantographarms 63 and 64, respectively, and toeach opposite pair of brackets I mount a non-rotatable friction track inthe form of an annulus concentric with the propeller shaft and free ofengagement therewith. I indicate the forward friction track as 68 'andthe rear friction track as 69, and

their friction faces are of any suitable material, disposed at a beveland spaced to co-act with one side or the other of a friction wheel 70,which is mounted upon a shaft 71 that pierces at right angles thepropeller shaft and is suitably journaled thereon. On this shaft 71within the propeller shaft I mount a worm 72, meshing with a worm gear73 fast on a cross shaft 74 inside the propeller shaft, on which issecured -a sprocket 75 connected by a sprocket chain 76 with a sprocket77 fast on another shaft 78 within the propeller shaft.

A second sprocket on this shaft 78 acts.

through a chain 79 and a sprocket 80 to drive a shaft 81 which extendsthrough the propeller shaft and through the spider hub and is providednear each end between the flanges 8 and 9 of the spider with a worm 82meshing with its respective worm gear 83. These worm gears 83 aremounted each on a shaft' 84 suitably journaled in al block 84 cast onthe web of the spider wheel, and each carries on its forward end pinions85 meshing with the pinion teeth 86 about the periphery of a master gearwheel 11.

Referring now to Fig. 7 there is shown diagrammatically the propellerblade elements 17 and 18 rotating in the plane and in the direction ofthe arrow XY, the relative direction of the wind currents being shown bythe arrows W. The vane pilot 24 is shown forward of the propeller bladeand in line with the relative direction of the approaching windcurrents. It will be readily seen that should the relative direction ofthe wind currents change, the circuit closing stem 25 will bel swung 1naccordance with said change in a direction to complete one of thecircuits, as already described, 'and change the angles of the bladeelement to conform to the changeddirection of the wind currents.

Referring to Fig. 8, the direction of rotation and velocity of thepropeller blades, as shown in Fig. 7, are indicated graphically by theline AC; the direction and velocity of the wind currents are indicatedgraphically by the line BC; and the relative direction and velocity ofthe wind currents are indicated by the resultant BA. It will be seenthat should the velocity of the propeller blades be changed to shortenor lengthen the line AC, or the direction or velocity of the windcurrents change, to change the length of the line BC or to change theangle of the line BC with the line AC, the resultant AB will be changedand the angle BAC will be changed. Any change in the angle BAC affectsthe vane pilot 24 and effects 'a' completion of one of the electriccircuits through the member 25 and consequent adjustment of the pitch ofthe propeller blades in a manner which will now be described.

In `the operation of my apparatus, first disregarding the action of thepilot, the motor drives through the main ropeller shaft to the impellerspider and t rough the latter serves to drive the several impellerblades, which are held in the desired pitch relationship by the meshingof their respective pinions 13 with the master gear 10, and this 4drivecontinues without change in position of parts so long as the air strikesthe impeller to throw the double-throw switch so as to ent ergize theset-works solenoid 55 to move its core and the set vworks to the rightor the left so as to bring the forward orthe rear friction track intocontact with the friction wheel 70,

which, being mounted to revolve with the -1 propeller shaft, will berotated clockwise or counter-clockwise according to whether it engagesthe forward or rear friction track. The rotation thus imparted to theshaft 72 of friction wheel 71 will, through the transmission describedwithin the propeller shaft, turn the worm-carrying shaft 81, and throughits worm and gear connections shown will acttoy rotate the master gearclockwise or counter-clockwise so as to turn the impeller blade shaftsand 'change the pitch of the impeller blades in the direction requiredto restore the condition of tangency. Brielly stated, as the pilot isdeflected b nontangential currents it will, through t einstrumentalities described, change the pitch of the impeller bladesuntil Athey will strike the air in true tangency and this can be main--tained within the predetermined limits allowed for the reversal ofcircuits by the/'pilot stem. j

If operated in a calm, the electrical governor promptly starts adjustingthe impeller blades to a condition of tangency at their leading edge.When true 4tangency is established it should be easily recognized by thehealthy whistle of the impeller blades. Any variation in operatingconditions will cause the electrical governor to make readjustments thatwill result in a condition of tangency. As the motor slows down thetendency is for the impeller blades to settle back into zero position,i. e., in a position parallel in the spider. When the propeller ismounted on a plane where the velocity of approaching air is constantlychanging, the electrical governor will perfectly meet the changingconditions irrespective of what they are, be it a change in R. P. M., orchange in velocity of approach of the air. If the motor slows down, thetendenc is for the impeller blades, under direction o the governor, toapproach the 90 position. But irrespective of everything, as regardspossible operating conditions, as long as `the motor is turning over7this efliciency propeller is eXercisin a drawbar pull which will be amaximum or power consumed and will -bear a mathematical relation to theR. P. M.

The reason for theefliciency of the propeller is the avoidance of eddycurrents, and the creation of a condition of steady, easy, acceleratedfiowage of air in very large volumes with low change in velocity. Thescrew propellers of recent design with their fixed impeller blades, ofunalterable pitch, their enormously high number of R. P. M.s, representand are, only a nice refinement of the original idea.

The hereindescribed propeller is not a screw propeller in any acceptedsense. It is an efficient tangency propeller, delivering a maximum ofdraw-bar pull with a minimum of power consumption and witha low R.

.The blades in their structure are unusually strong, will obtain a veryefficient purchase 4 on theair, and the angles 20 at their tips willtend to hold' the air from radial movement off the blades responsive tocentrifugal pressure and the angular disposition of the blades. Thepantograph mechanism shown is typical of any comparatively inexpensivemeans which can be utiliz/ed to shift the nonrotatable frictionelementinto engagement with the friction Wheel according to thedirection in which it is desired to rotate the latter responsive to itsrevolution with the propellershaft.

While it is contemplated that my invention should maintain anapproximately exact condition of tangency vbetween the air currents andthe blade, nevertheless it is obvious that it can be easily adapted tomaintain any desired angle of incidence, and where the expressiontangency is used it contemplates any predetermined departure therefrom@Though I have described with great pari ticularity the details of theembodiment of the invention herein shown, it is not to be construed thatI am limited thereto, as changes in arrangement and substitution ofequivalents may be made by those skilled in the art without departingfrom the invention as defined in the appended claims.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent, is

1. A propeller mechanism, comprising a plurality of impeller blades, ashaft on which said blades are rotatably mounted for change in pitch,and means independent of the blades Vand responsive to variation in theapproach of fluid currents to the blades to maintain a condition oftangency between the blades and the approaching fluid currents.

2. A propeller mechanism, comprising a plurality of impeller blades, ashaft on which said blades are rotatably mounted for change in pitch,and means movable independently of the bladesand responsive to variationin the approach of fluid currents from a condition of tangency to theblades to change the pitch of the blades automatically until substantialtangency is restored. i 3. A propeller mechanism comprising a shafthaving impeller blades mounted thereon for change in pitch, andmechanism common to a plurality of blades and automatically responsiveto the direction of approach of air currents to the blades for changingthe pitch of the blades.

-t. A propeller mechanism comprising a shaft having .blades mountedthereon for change in pitch, a pilot rotatable with the blades andmovable responsive tov departure ofthe direction of approach of the Huidcurrents from tangency to the blades, and mechanism responsive to pilotmovements for automatically changing the pitch of the blades to maintaintangency.

5. A propeller mechanism comprising a shaft having blades mountedthereon for change in pitch, a pilot rotatable with the blades andmovable responsive to departure. of the fluid currents from tangency tothe blades, and electromagnetic-ally controlled mechanism for changingthe pitch Vof the blades to maintain tangency.

6. aA propeller mechanism comprising a propeller shaft, a wheel mountedthereon carrying impeller blades, gear means to control and vary thepitch of the blades, and a pilot-controlled mechanism adapted,responsive to the direction of approach of fluid currents from acondition of tangency to the blades, to change the pitch of the bladesto restore tangency.

7. propeller mechanism, comprising a tubular propeller shaft, means tomount impeller blades on the shaft free for change in pitch, mechanismrotatable with the propeller shaft for changing the pitch of the bladescomprising a revoluble friction drive wheel,

a transmission therefrom to the various impeller blades, stationaryfriction means adapted to co-act with the revoluble friction on oppositesides to drive it in the desired direction, and means responsive to apilot for controlling the direction of drive of the friction wheel.

8. A propeller mechanism, comprising ra propeller shaft, impeller bladesmounted thereon free for change in pitch, and mechanism for varying thepitch of the blades comprising a rotatable friction wheel revoluble withthe propeller shaft, coacting non-rotatable Y friction elements adaptedto be brought into engagement, one at a time, with the friction wheel torotate it in the desired direction as it revolves, a transmissioncontrolled by the rotation of the friction wheel for adjusting the pitchof the blades, and a pilot controlled mea-ns for engaging the desiredfriction element with said friction wheel.

9. A propeller mechanism according to claim 8,' in which thetransmission mecha- .nism comprises a master gear, gears on eachimpeller blade meshing the master gear, and a drive means connecting therevoluble friction wheel with the master gear.

l0. A propeller mechanism according t'o claim 8, in which thetransmission mechanism comprises a master gear, gears on each impellerblade meshing the master gear, a drive means connecting the revolublefriction wheel with the master gear which comprises in part mechanismhoused in the propeller shaft and a transmissionleading therefrom andincluding a worm drive to the master gear.

l1. A propeller mechanism comprising im- Y peller blades mounted forchange in pitch and having individual controlling gears, a master gearmeshing said gears, and vane pilot controlled means to move the mastergear and vary the pitch .of the blades comed in the spider and havinggears meshing lsaid master gear, a pilot mounted in advance of one o'fthe impeller blades and adapted to be displaced when the fluid medium isnot striking the blades as desired, and circuit control mechanismresponsive to the displacement of the pilot for magneticallycontrolling, by movement of-the pantograph, the actuation of thefriction wheel.

13. In a propeller mechanism, blades mounted to rotate for change inpitch, a pilot independent of the blades and rotatable therewith andsensitive only to the approach prlsmg circuit closing means andelectromagnetic means responsive to the circuit closing means forcontrolling the adjustment of the master gear.

12. In a propeller mechanism, a tubular propeller shaft, a frictionwheel shaft mounted at right angles to and projecting through thepropeller shaft, a friction wheel rotatable with its said shaft andrevoluble with the propeller shaft, a pair of friction tracks disposedon each side of the friction wheel and normally disengaged therefrom,magnetically controlled pantograph mechanism for moving the desiredtrack into engagement with said friction wheel, a transmission from thefriction wheel shaft to the forward end of the propeller shaft, a crossshaft driven by said transmission, an impeller spider in which saidcross shaft is mounted, a master gear connected by a worm drive withsaid cross shaft, impeller blades rotatably mount-

